Remote fob problem

Can anyone help please ?
The battery went flat on my S reg 300tdi disco due to an interior light being left on. Opened the door using the key and fully charged the battery. Lights on the dash would come on but wouldn't turn over. Remote wouldn't lock or unlock the doors. Alarm then went off. The spare remote locks and unlocks the doors and the vehicle now starts fine, but... the original remote does not work. Worked fine up to now. Is it out of sync ? Any ideas ? thanks

Gould be, try pressing the lock button four times assuming the fobs battery is ok.
U can find info and more is in the owners handbook, also iits already in the forum threads on this subject more than once.